Commercial preparation of many different food and non-food products requires use of pumping equipment suited for pumping materials which do not readily flow or are otherwise difficult to pump. For example, food products such as cheeses, lards and shortenings, ground meat, sugars, and doughs, typically require the use of specialized multi-stage pumping devices for effecting desired movement of such materials. Similarly, non-food products such as adhesives, soaps, putties and caulking compounds, and the like require the use of specialized pumping equipment if efficient handling is to be achieved.
A typical construction for a multi-stage pumping apparatus for use with such materials comprises a pair of generally horizontally arranged, cooperating screw augers. In such an arrangement, each auger is typically provided with a helical, so-called Archimedian flight, with rotation of the augers together acting to advance material axially of the augers by non-positive displacement pumping. The screw augers are typically arranged to move material through an inwardly tapered transition element having a generally oval-shaped inlet which receives material from both of the augers. Typically, a positive-displacement pump is provided immediately downstream of the transition element, with the positive-displacement pump including cooperating, multi-lobular rotors which positively pump the material to associated downstream equipment.
Infeed of material into this type of pump construction is typically effected via an infeed opening which opens downwardly to the side-by-side screw augers. Since these types of pumps are frequently used with material which does not flow readily, a paddle-like, so-called power feed roller may be operatively positioned at the infeed opening. Such a power feed roller ordinarily is rotatable about an axis spaced above and transverse to the parallel axes of the screw augers, with the feed roller including paddle-like vanes which engage the material in the infeed opening and act to drive it downwardly toward the screw augers.
While the above-described pump construction has been widely used, the shortcomings in its design will be readily appreciated. In view of the various driven screw augers, positive displacement rotors, and power feed roller, such an apparatus typically requires multiple drive motors, as well as suitable drive trains for powering the various movable components. This, of course, further adds to the already considerable expense associated with the relatively large number of components which are required. Further, the infeed of this type of apparatus can be subject to problem of "tunneling" or "bridging". These terms refer to a "carving out" action by the screw augers and/or the power feed roller on a mass of material at the infeed, whereby material movement is substantially interrputed.
In view of the widespread need for a pumping apparatus which can move materials which are otherwise very difficult to pump, it is desirable to provide a pumping apparatus particularly suited for efficiently handling such materials. Preferably, such an apparatus should not only lend itself to reliable and uninterrupted operation, but further is preferably configured for economical manufacture and convenient, versatile use.